Dialkyl dicarbonates as blowing agents for polymers

Abstract

The present invention pertains to a composition of matter and to a method of using the composition to produce foamed plastics, wherein a major, auxiliary source of blowing agent for the foam is the decomposition of dialkyl dicarbonates. The dialkyl dicarbonates can be decomposed over temperatures ranging from about 10 DEG C. to about 45 DEG C. when used in combination with particular tertiary amine decomposition catalysts.

What is claimed is: 
     
       1. A method of producing polymeric foams wherein at least one of the blowing agents used is a catalyzed blowing agent capable of generating carbon dioxide gas at about room temperature, said method comprising the steps of: (a) providing a polyurethane and at least one blowing agent comprising a dicarbonate having alkyl substituent end groups,   (b) combining said dicarbonate compound with at least one dicarbonate decomposition catalyst comprising a tertiary amine having at least one sterically accessable nitrogen which exhibits nucleophilicity; and   (c) using the combination of said blowing agent and said decomposition catalyst to initiate the generation of carbon dioxide gas at about room temperature.   
     
     
       2. The method of claim 1 wherein said combination of blowing agent with said decomposition catalyst is tailored to the reaction rate of the polymeric reactants used to generate the polymeric portion of said foam, whereby the gellation of said polymeric portion of said foam and the generation of said carbon dioxide gas by said dicarbonate produces a polymeric foam having designated characteristics. 
     
     
       3. The method of claim 1 wherein said decomposition catalyst is selected from the group consisting of molecules having a bridgehead nitrogen, tertiary 4-amino derivatives of pyridine, dimethyl alkyl amine, poly dimethyl alkyl amine containing a linking group, and combinations thereof. 
     
     
       4. The method of claim 1 wherein said blowing agent includes a linking group between the di-carbonate portions of said molecule. 
     
     
       5. The method of claim 1 wherein said alkyl substituent contains from 1-10 carbon atoms. 
     
     
       6. The method of claim 5 wherein said alkyl substituent is halogenated or polyhalogenated. 
     
     
       7. The method of claim 5 wherein at least one of said alkyl substituent groups is a tertiary alkyl. 
     
     
       8. The method of claim 1 wherein a linking group is present between the di-carbonate portions of said molecules. 
     
     
       9. The method of claim 7 wherein a linking group is present between the di-carbonate portions of said molecule. 
     
     
       10. The method of claim 1 wherein said polyurethane foam is produced according to a flexible formulation. 
     
     
       11. The method of claim 1 wherein said polyurethane foam is produced according to a rigid formulation. 
     
     
       12. The method of claim 1 wherein an additional blowing agent comprising a chlorofluorocarbon is used in combination with said dicarbonate blowing agent.